Nanosecond pulser bias compensation

ABSTRACT

A high voltage power system is disclosed. In some embodiments, the high voltage power system includes a high voltage pulsing power supply; a transformer electrically coupled with the high voltage pulsing power supply; an output electrically coupled with the transformer and configured to output high voltage pulses with an amplitude greater than 1 kV and a frequency greater than 1 kHz; and a bias compensation circuit arranged in parallel with the output. In some embodiments, the bias compensation circuit can include a blocking diode; and a DC power supply arranged in series with the blocking diode.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application claims priority to U.S. Provisional Patent ApplicationNo. 62/711,464 filed Jul. 27, 2018, titled “NANOSECOND PULSER SYSTEM,”which is incorporated by reference in its entirety.

This application claims priority to U.S. Provisional Patent ApplicationNo. 62/711,334 filed Jul. 27, 2018, titled “NANOSECOND PULSER THERMALMANAGEMENT,” which is incorporated by reference in its entirety.

This application claims priority to U.S. Provisional Patent ApplicationNo. 62/711,457 filed Jul. 27, 2018, titled “NANOSECOND PULSER PULSEGENERATION,” which is incorporated by reference in its entirety.

This application claims priority to U.S. Provisional Patent ApplicationNo. 62/711,347 filed Jul. 27, 2018, titled “NANOSECOND PULSER ADCSYSTEM,” which is incorporated by reference in its entirety.

This application claims priority to U.S. Provisional Patent ApplicationNo. 62/711,467 filed Jul. 27, 2018, titled “EDGE RING POWER SYSTEM,”which is incorporated by reference in its entirety.

This application claims priority to U.S. Provisional Patent ApplicationNo. 62/711,406 filed Jul. 27, 2018, titled “NANOSECOND PULSER BIASCOMPENSATION,” which is incorporated by reference in its entirety.

This application claims priority to U.S. Provisional Patent ApplicationNo. 62/711,468 filed Jul. 27, 2018, titled “NANOSECOND PULSER CONTROLMODULE,” which is incorporated by reference in its entirety.

This application claims priority to U.S. Provisional Patent ApplicationNo. 62/717,523 filed Aug. 10, 2018, titled “PLASMA SHEATH CONTROL FOR RFPLASMA REACTORS,” which is incorporated by reference in its entirety.

This application claims priority to U.S. Provisional Patent ApplicationNo. 62/789,523 filed Jan. 1, 2019, titled “EFFICIENT NANOSECOND PULSERWITH SOURCE AND SINK CAPABILITY FOR PLASMA CONTROL APPLICATIONS,” whichis incorporated by reference in its entirety.

This application claims priority to U.S. Provisional Patent ApplicationNo. 62/717,526 filed Jan. 1, 2019, titled “EFFICIENT ENERGY RECOVERY INA NANOSECOND PULSER CIRCUIT,” which is incorporated by reference in itsentirety.

BACKGROUND

In plasma deposition systems, a wafer is often electrostatically securedwith a chuck in a chamber. Plasmas are created within the chamber andhigh voltage pulses are introduced to accelerate ions within the plasmaonto the wafer. If the electric potential between the chuck and thewafer exceeds a certain voltage threshold (e.g., about ±2 kV), theforces on the wafer may be large enough to damage or break the wafer.

SUMMARY

Embodiments of the invention include a method and circuits for biascompensation in a high voltage plasma chamber such as, for example, aplasma deposition system, semiconductor fabrication system, plasmasputtering system, etc.

A high voltage power system is disclosed. In some embodiments, the highvoltage power system includes a high voltage pulsing power supply (e.g.,a nanosecond pulser); a transformer electrically coupled with the highvoltage pulsing power supply; an output electrically coupled with thetransformer. The output of the high voltage power system can beconfigured to output high voltage pulses with an amplitude greater than1 kV, 2 kV, 5 kV, 10 kV, 25 kV, etc. and a frequency greater than 1 kHz;and a bias compensation circuit arranged in parallel with the output. Insome embodiments, the bias compensation circuit can include a blockingdiode; and a DC power supply arranged in series with the blocking diode.In some embodiments, the high voltage power system can include a biascapacitor arranged across at least the DC power supply. In someembodiments, the high voltage power system may include a biascompensation inductor arranged in series with the high voltage switch.

In some embodiments, the high voltage pulsing power supply comprises ananosecond pulser and a transformer. In some embodiments, the highvoltage power supply comprises a plurality of switches arranged inseries and a transformer. In some embodiments, the high voltage powersupply include a radio-frequency power supply such as, for example, anRF generator.

In some embodiments, the bias compensation circuit comprises a highvoltage switch disposed across the blocking diode, wherein the highvoltage switch is configured to be open when the high voltage pulsingpower supply is pulsing, and wherein the high voltage switch isconfigured to be closed when the high voltage pulsing power supply isnot pulsing.

In some embodiments, the high voltage switch comprises a plurality ofswitches arranged in series. In some embodiments, the bias compensationinductor has an inductance less than about 100 μH. In some embodiments,the output is coupled with a plasma such as, for example, via anelectrode that is capacitively coupled with the plasma.

In some embodiments, a high voltage power system may include a highvoltage pulsing power supply; an output electrically coupled with thetransformer and configured to output high voltage pulses with anamplitude greater than 2 kV and a frequency greater than 2 kHz; ablocking diode; a DC power supply; arranged in series with the blockingdiode, the blocking diode and the DC power supply arranged in parallelwith the output; and a high voltage switch coupled across the blockingdiode, wherein the high voltage switch is configured to turn off whenthe high voltage switching power supply is pulsing (e.g., duringbursts), and the high voltage switch is turned on when the high voltageswitching power supply is not pulsing (e.g., in between bursts).

In some embodiments, the high voltage power system may also include abias compensation capacitor arranged across at least the DC power supplyhaving a capacitance less than about 500 μF, 250 μF, 100 μF, 50 μF, 25μF, 10 μF, etc.

In some embodiments, the blocking diode, the DC power supply, and thehigh voltage switch comprise a bias compensation circuit that isarranged in the high voltage power system across the output.

In some embodiments, the output may include a plasma load. In someembodiments, the DC power supply provides about ±5 kV, ±4 kV, ±3 kV, ±2,kV, ±1 kV, etc.

In some embodiments, the high voltage switch is configured to be openwhen the high voltage pulsing power supply is pulsing, and wherein thehigh voltage switch is configured to be closed when the high voltagepulsing power supply is not pulsing.

In some embodiments, the high voltage switch includes a snubber circuit.

Some embodiments may include a method comprising opening a biascompensation switch that is arranged in series with a DC power supply,the bias compensation switch and the DC power supply being arrangedacross a load; pulsing a high voltage power supply with a high voltageand a high frequency into the load; closing the bias compensationswitch; and not pulsing the high voltage power supply.

Some embodiments include a high voltage power system comprising aplurality of switches; a transformer; an output configured to outputhigh voltage pulses with an amplitude greater than 2 kV and a frequencygreater than 1 kHz; a blocking diode; and a bias capacitor.

Some embodiments include a high voltage power system comprising: a highvoltage switching power supply; an output configured to output highvoltage pulses with an amplitude greater than 2 kV and a frequencygreater than 1 kHz; a blocking diode; a bias capacitor; and a highvoltage switch coupled across the blocking diode, wherein the highvoltage switch is off when the high voltage switching power supply ispulsing, and the high voltage switch is on when the high voltageswitching power supply is not pulsing.

Some embodiments include a high voltage power system producing an outputthat creates a plasma within a wafer deposition chamber such that thevoltage potential between the wafer and a chuck is about 2 kV duringperiods with the high voltage power system is pulsing and not pulsing.

These illustrative embodiments are mentioned not to limit or define thedisclosure, but to provide examples to aid understanding thereof.Additional embodiments are discussed in the Detailed Description, andfurther description is provided there. Advantages offered by one or moreof the various embodiments may be further understood by examining thisspecification or by practicing one or more embodiments presented.

BRIEF DESCRIPTION OF THE FIGURES

These and other features, aspects, and advantages of the presentdisclosure are better understood when the following Detailed Descriptionis read with reference to the accompanying drawings.

FIG. 1 is a circuit diagram of a high voltage power system with a plasmaload according to some embodiments.

FIG. 2 shows example waveforms produced by a high voltage power systemaccording to some embodiments.

FIG. 3 is a circuit diagram of a high voltage power system with a plasmaload according to some embodiments.

FIG. 4 shows example waveforms produced by a high voltage power systemaccording to some embodiments.

FIG. 5 is a circuit diagram of a high voltage power system with a plasmaload according to some embodiments.

FIG. 6 shows example waveforms produced by a high voltage power systemaccording to some embodiments.

FIG. 7 is a circuit diagram of a high voltage power system with a plasmaload according to some embodiments.

FIG. 8 shows example waveforms produced by a high voltage power systemaccording to some embodiments.

FIG. 9 is a circuit diagram of a high voltage power system with a plasmaload according to some embodiments.

FIG. 10 shows example waveforms from a high voltage power systemaccording to some embodiments.

FIG. 11A shows example waveforms from a high voltage power systemaccording to some embodiments.

FIG. 11B shows example waveforms from a high voltage power systemaccording to some embodiments.

FIG. 12 is a circuit diagram of a high voltage power system with aplasma load according to some embodiments.

FIG. 13 is a circuit diagram of a high voltage power system with aplasma load according to some embodiments. Snubbers and voltage divisionresistors

FIG. 14 is a circuit diagram of a high voltage power system according tosome embodiments.

FIG. 15 is a block diagram of a high voltage switch with isolated poweraccording to some embodiments.

FIG. 16 shows an example waveform from a high voltage power systemaccording to some embodiments.

FIG. 17 shows an example waveform from a high voltage power systemaccording to some embodiments.

FIG. 18 shows an example waveform from a high voltage power systemaccording to some embodiments.

FIG. 18 shows an example waveform from a high voltage power systemaccording to some embodiments.

FIG. 19 is a circuit diagram of a high voltage power system with aplasma load according to some embodiments.

DETAILED DESCRIPTION

In plasma deposition systems a wafer is often electrostatically securedwith a chuck in a deposition chamber. Plasmas are created within thechamber and high voltage pulses are introduced to accelerate ions withinthe plasma onto the wafer. If the electric potential between the chuckand the wafer exceeds a certain voltage threshold (e.g., about 2 kV),the forces on the wafer may be large enough to damage or break thewafer. In addition, it can be beneficial to introduce higher voltagepulses into the chamber to increase trench depth, improve quality, or tospeed up the etching process. The introduction of high and highervoltage pulses into the plasma within the deposition chamber can affectthe electric potential between the chuck and the wafer and damage orbreak the wafers.

Systems and methods are disclosed to ensure the voltage between a waferand a chuck is near or below the threshold (e.g., about 2 kV) duringperiods of high voltage pulsing and during periods without high voltagepulsing. These systems, for example, may also limit the self-biasing ofthe wafer when using high-voltage radio-frequency power supplies. Thesesystems and methods, for example, may compensate for voltage changes toensure the voltage between the chuck and wafer does not exceed thevoltage threshold.

In some embodiments, a high voltage power system may produce pulsevoltages that are introduced into the plasma with amplitudes of about 1kV, 2 kV, 5 kV, 10 kV, 15 kV, 20 kV, 30 kV, 40 kV, etc. In someembodiments, a high voltage power system may switch with frequencies upto about 500 kHz. In some embodiments, a high voltage power system mayprovide single pulses of varying pulse widths from about 50 nanosecondsto about 1 nanosecond. In some embodiments, a high voltage power systemmay switch at frequencies greater than about 10 kHz. In someembodiments, a high voltage power system may operate with rise timesless than about 20 ns.

As used throughout this document, the term “high voltage” may include avoltage greater than about 1 kV, 10 kV, 20 kV, 50 kV, 100 kV, 1,000 kV,etc.; the term “high frequency” may be a frequency greater than about 1kHz, 10 kHz, 100 kHz, 200 kHz, 500 kHz, 1 MHz, etc.; the term “highrepetition rate” may be a rate greater than about 1 kHz, 10 kHz, 100kHz, 200 kHz, 500 kHz, 1 MHz, etc., the term “fast rise time” mayinclude a rise time less than about 1 ns, 10 ns, 50 ns, 100 ns, 250 ns,500 ns, 1,000 ns, etc.; the term “fast fall time” may include a falltime less than about 1 ns, 10 ns, 50 ns, 100 ns, 250 ns, 500 ns, 1,000ns, etc.; the term “low capacitance” may include capacitance less thanabout 1.0 pF, 10 pF, 100 pF, 1,000 pF, etc.; the term “low inductance”may include inductance less than about 10 nH, 100 nH, 1,000 nH, 10,000nH, etc.; and the term short pulse width may include pulse widths lessthan about 10,000 ns, 1,000 ns, 500 ns, 250 ns, 100 ns, 20 ns, etc.

FIG. 1 is a circuit diagram of a high voltage power system with a plasmaload 100 according to some embodiments. The high voltage power systemwith a plasma load 100 can be generalized into six stages (these stagescould be broken down into other stages or generalized into fewer stagesor may or may not include the components shown in the figure). The highvoltage power system with a plasma load 100 includes a pulser stage 101,a resistive output stage 102, a lead stage 103, a DC bias circuit 104, asecond lead stage 105, and a load stage 106. The pulser stage 101, theresistive output stage 102, or the DC bias circuit 104 may comprise ahigh voltage power system. The lead stage 103 or the second lead stage105 may also be included in the high voltage power system. Whereas theload stage 106 may include a plasma load.

In some embodiments, the high voltage power system with a plasma load100 (or the pulser stage 101) can introduce pulses into the load stagewith voltages greater than 1 kV, 10 kV, 20 kV, 50 kV, 100 kV, 1,000 kV,etc., with rise times less than about 1 ns, 10 ns, 50 ns, 100 ns, 250ns, 500 ns, 1,000 ns, etc. with fall times less than about 1 ns, 10 ns,50 ns, 100 ns, 250 ns, 500 ns, 1,000 ns, etc. and frequencies greaterthan about 1 kHz, 10 kHz, 100 kHz, 200 kHz, 500 kHz, 1 MHz, etc.

In some embodiments, the pulser stage 101, for example, may include anydevice capable of producing pulses greater than 500 V, peak currentgreater than 10 Amps, or pulse widths of less than about 10,000 ns,1,000 ns, 100 ns, 10 ns, etc. As another example, the pulser stage 101may produce pulses with an amplitude greater than 1 kV, 5 kV, 10 kV, 50kV, 200 kV, etc. As another example, the pulser stage 101 may producepulses with rise times or fall times less than about 5 ns, 50 ns, or 300ns, etc.

In some embodiments, the pulser stage 101 can produce a plurality ofhigh voltage bursts. Each burst, for example, can include a plurality ofhigh voltage pulses with fast rise times and fast fall times. Theplurality of high voltage bursts, for example, can have a burstrepetition frequency of about 10 Hz to 10 kHz. More specifically, forexample, the plurality of high voltage bursts can have a burstrepetition frequency of about 10 Hz, 100 Hz, 250 Hz, 500 Hz, 1 kHz, 2.5kHz, 5.0 kHz, 10 kHz, etc.

Within each of the plurality of high voltage bursts, the high voltagepulses can have a pulse repetition frequency of about 1 kHz, 10 kHz, 100kHz, 200 kHz, 500 kHz, 1 MHz, etc.

In some embodiments, the burst repetition frequency time from one bursttill the next burst. Frequency at which the bias compensation switch isoperated.

In some embodiments, the pulser stage 101 can include one or more solidstate switches S1 (e.g., solid state switches such as, for example,IGBTs, a MOSFETs, a SiC MOSFETs, SiC junction transistors, FETs, SiCswitches, GaN switches, photoconductive switches, etc.) coupled with avoltage source V2. In some embodiments, the pulser stage 101 can includeone or more source snubber resistors R3, one or more source snubberdiodes D4, one or more source snubber capacitors C5, or one or moresource freewheeling diodes D2. One or more switches and or circuits canbe arranged in parallel or series.

In some embodiments, the pulser stage 101 can produce a plurality ofhigh voltage pulses with a high frequency, fast rise times, fast falltimes, at high frequencies, etc. The pulser stage 101 may include one ormore nanosecond pulsers.

In some embodiments, the pulser stage 101 may comprise a high voltagepulsing power supply.

The pulser stage 101 may, for example, include any pulser described inU.S. patent application Ser. No. 14/542,487, titled “High VoltageNanosecond Pulser,” which is incorporated into this disclosure in itsentirety for all purposes. The pulser stage 101 may, for example,include any pulser described in U.S. Pat. No. 9,601,283, titled“Efficient IGBT Switching,” which is incorporated into this disclosurein its entirety for all purposes. The pulser stage 101 may, for example,include any pulser described in U.S. patent application Ser. No.15/365,094, titled “High Voltage Transformer,” which is incorporatedinto this disclosure in its entirety for all purposes.

The pulser stage 101 may, for example, include a high voltage switch(e.g., see FIG. 3). For example, the pulser stage 101 may include thehigh voltage switch 1500 described in FIG. 15. As another example, thepulser stage 101 may, for example, include any switch described in U.S.patent application Ser. No. 16/178,565, filed Nov. 1, 2018, titled “HighVoltage Switch with Isolated Power,” which is incorporated into thisdisclosure in its entirety for all purposes.

In some embodiments, the pulser stage 101 can include a transformer T2.The transformer T2 may include a transformer core (e.g., a toroid ornon-toroid core); at least one primary winding wound once or less thanonce around the transformer core; and a secondary winding wound aroundthe transformer core a plurality of times.

In some embodiments, the transformer T2 may include a single-turnprimary winding and a multi-turn secondary windings around a transformercore. The single-turn primary winding, for example, may include one ormore wires wound one or fewer times around a transformer core. Thesingle-turn primary winding, for example, may include more than 2, 10,20, 50, 100, 250, 1200, etc. individual single-turn primary windings. Insome embodiments, the primary winding may include a conductive sheet.

The multi-turn secondary winding, for example, may include a single wirewound a plurality of times around the transformer core. The multi-turnsecondary winding, for example, may be wound around the transformer coremore than 2, 10, 25, 50, 100, 250, 500, etc. times. In some embodiments,a plurality of multi-turn secondary windings may be wound around thetransformer core. In some embodiments, the secondary winding may includea conductive sheet.

In some embodiments, the high-voltage transformer may be used to outputa voltage greater than 1,000 volts with a fast rise time of less than150 nanoseconds or less than 50 nanoseconds, or less than 5 ns.

In some embodiments, the high-voltage transformer may have a lowimpedance and/or a low capacitance. For example, the high-voltagetransformer has a stray inductance of less than 100 nH, 50 nH, 30 nH, 20nH, 10 nH, 2 nH, 100 pH as measured on the primary side and/or thetransformer has a stray capacitance of less than 100 pF, 30 pF, 10 pF, 1pF as measured on the secondary side.

The transformer T2 may comprise a transformer as disclosed in U.S.patent application Ser. No. 15/365,094, titled “High VoltageTransformer,” which is incorporated into this document for all purposes.

In some embodiments, a plurality of pulsers can be combined either orboth in parallel or series. In some embodiments, the pulser stage 101may be coupled with the resistive output stage 102 across the inductorL1 and/or the resistor R1. In some embodiments, inductor L1 may includean inductance of about 5 μH to about 25 μH. In some embodiments, theresistor R1 may include a resistance of about 50 ohms to about 250 ohms.Each of the plurality of pulser stages 101 may each also include eitheror both blocking diode D4 or diode D6. In some embodiments, thecapacitor C4 may represent the stray capacitance of the diode D6.

In some embodiments, the resistive output stage 102 can dischargecapacitive loads (e.g., the wafer and/or the plasma).

In some embodiments, the resistive output stage 102 may include one ormore inductive elements represented by inductor L1 and/or inductor L5.The inductor L5, for example, may represent the stray inductance of theleads in the resistive output stage 102 and may have an inductance lessthan about 500 nH, 250 nH, 100 nH, 50 nH, 25 nH, 10 nH, etc. Theinductor L1, for example, may be set to minimize the power that flowsfrom the pulser stage 101 into resistor R1.

In some embodiments, the resistive output stage 102 may include at leastone resistor R1, which may, for example, comprise a plurality ofresistors in series or parallel, that can discharge a load (e.g., theplasma sheath capacitance).

In some embodiments, the resistor R1 may dissipate charge from the loadstage 106, for example, on fast time scales (e.g., 1 ns, 10 ns, 50 ns,100 ns, 250 ns, 500 ns, 1,000 ns, etc. time scales). The resistance ofresistor R1 may be low to ensure the pulse across the load stage 106 hasa fast fall time t_(f).

In some embodiments, the resistive output stage 102 may be configured todischarge over about 1 kilowatt of average power during each pulse cycleand/or a joule or less of energy in each pulse cycle. In someembodiments, the resistance of the resistor R1 in the resistive outputstage may be less than 200 ohms.

The capacitor C11 may represent the stray capacitance of the resistor R1(or the plurality of resistors arranged in series or parallelrepresented by resistor R1) including the capacitance of the arrangementof series and/or parallel resistors. The capacitance of straycapacitance C11, for example, may be less than 500 pF, 250 pF, 100 pF,50 pF, 10 pF, 1 pF, etc. The capacitance of stray capacitance C11, forexample, may be less than the load capacitance such as, for example,less than the total capacitance of C2, C3, and/or C9 or the individualcapacitance of C2, C3, or C9.

In some embodiments, the resistive output stage 102 may include acollection of circuit elements that can be used to control the shape ofa voltage waveform on a load. In some embodiments, the resistive outputstage 102 may include passive elements only (e.g., resistors,capacitors, inductors, etc.). In some embodiments, the resistive outputstage 102 may include active circuit elements (e.g., switches) as wellas passive circuit elements. In some embodiments, the resistive outputstage 102, for example, can be used to control the voltage rise time ofa waveform and/or the voltage fall time of a waveform.

In some embodiments, a resistive output stage 102 can be used incircuits with pulses having either or both high pulse voltage (e.g.,voltages greater than 1 kV, 10 kV, 20 kV, 50 kV, 100 kV, etc.) or highfrequencies (e.g., frequencies greater than 1 kHz, 10 kHz, 100 kHz, 200kHz, 500 kHz, 1 MHz, etc.).

In some embodiments, the resistive output stage 102 may be selected tohandle high average power, high peak power, fast rise time fast falltimes. For example, the average power rating might be greater than about0.5 kW, 1.0 kW, 10 kW, 25 kW, etc., or the peak power rating might begreater than about 1 kW, 10 kW, 100 kW, 1 MW, etc.

In some embodiments, the resistive output stage 102 may include a seriesor parallel network of passive components. For example, the resistiveoutput stage 102 may include a series of a resistor, a capacitor, and aninductor. As another example, the resistive output stage 102 may includea capacitor in parallel with an inductor and the capacitor-inductorcombination in series with a resistor.

In some embodiments, the blocking diode D1, for example, may ensurecurrent flows through the resistor R1. The capacitor C8, for example,may represent the stray capacitance of the blocking diode D1.

In some embodiments, the resistive output stage 102 may be replaced byan energy recovery circuit or any other sink stage or any othercircuitry that can quickly sink charge from the plasma on fast timescales.

In some embodiments, the lead stage 103 may represent either or both theleads or traces between the resistive output stage 102 and the DC biascircuit 104. Either or both the inductor L2 or the inductor L6 mayrepresent the inductance with either or both the leads or traces.

In this example, the DC bias circuit 104 does not include any biascompensation. The DC bias circuit 104 includes an offset supply voltageV1 that may, for example, bias the output voltage either positively ornegatively. In some embodiments, the offset supply voltage V1, can beadjusted to change the offset between the wafer voltage and the chuckvoltage. In some embodiments, offset supply voltage V1 can have avoltage of about ±5 kV, ±4 kV, ±3 kV, ±2, kV, ±1 kV, etc. kV.

In some embodiments, the bias capacitor C12 can isolate (or separate)the DC bias voltage from either or both the resistive output stage orother circuit elements. The bias capacitor C12, for example, may allowfor a potential shift from one portion of the circuit to another. Insome embodiments, this potential shift may ensure that the electrostaticforce holding the wafer in place on the chuck remains below the voltagethreshold. The resistor R2 may isolate the DC bias supply from the highvoltage pulsed output from the pulser stage 101.

The bias capacitor C12, for example, 100 pF, 10 pF, 1 pF, 100 μF, 10 μF,1 μF, etc. The resistor R2, for example, may have a high resistance suchas, for example, a resistance of about 1 kOhm, 10 kOhm, 100 kOhm, 1MOhm, 10 MOhm, 100 MOhm, etc.

The second lead stage 105 represents circuit elements between the highvoltage power system and the load stage 106. The resistor R13, forexample, may represent the resistance of the leads or transmission linesthat connect from the output of the high voltage power system to theelectrode (e.g., the load stage 106). The capacitors C1, for example,may represent stray capacitance in the leads or transmissions line.

In some embodiments, the load stage 106 may represent an idealized oreffective circuit for semiconductor processing chamber such as, forexample, a plasma deposition system, semiconductor fabrication system,plasma sputtering system, etc. The capacitance C2, for example, mayrepresent the capacitance of the chuck upon which the wafer may sit. Thechuck, for example, may comprise a dielectric material. For example, thecapacitor C1 may have small capacitance (e.g., about 10 pF, 100 pF, 500pF, 1 nF, 10 nF, 100 nF, etc.).

The capacitor C3, for example, may represent the sheath capacitancebetween the plasma and the wafer. The resistor R6, for example, mayrepresent the sheath resistance between the plasma and the wafer. Theinductor L2, for example, may represent the sheath inductance betweenthe plasma and the wafer. The current source 12, for example, may berepresent the ion current through the sheath. For example, the capacitorC1 or the capacitor C3 may have small capacitance (e.g., about 10 pF,100 pF, 500 pF, 1 nF, 10 nF, 100 nF, etc.).

The capacitor C9, for example, may represent capacitance within theplasma between a chamber wall and the top surface of the wafer. Theresistor R7, for example, may represent resistance within the plasmabetween a chamber wall and the top surface of the wafer. The currentsource I1, for example, may be representative of the ion current in theplasma. For example, the capacitor C1 or the capacitor C9 may have smallcapacitance (e.g., about 10 pF, 100 pF, 500 pF, 1 nF, 10 nF, 100 nF,etc.).

As used in this document the plasma voltage is the voltage measured fromground to circuit point 123; the wafer voltage is the voltage measuredfrom ground to circuit point 122 and may represent the voltage at thesurface of the wafer; the chucking voltage is the voltage measured fromground to circuit point 121; the electrode voltage is the voltagemeasure from ground to circuit point 124; and the input voltage is thevoltage measured from ground to circuit point 125.

FIG. 2 shows example waveforms produced by the high voltage power systemwith a plasma load 100. In these example waveforms, the pulse waveform205 may represent the voltage provided to the load stage 106. As shown,the pulse waveform 205, which is the voltage at circuit point 124,produces a pulse with the following qualities: high voltage (e.g.,greater than about 4 kV as shown in the waveform), a fast rise time(e.g., less than about 200 ns as shown in the waveform), a fast falltime (e.g., less than about 200 ns as shown in the waveform), and shortpulse width (e.g., less than about 300 ns as shown in the waveform). Thewaveform 210 may represent the voltage at circuit point 122, forexample, at the surface of the wafer. The waveform 215 represent thecurrent flowing through the plasma, for example, the current throughinductor L2.

During the transient state (e.g., during an initial number of pulses notshown in the figure), the high voltage pulses from the pulser stage 101charge the capacitor C2. Because the capacitance of capacitor C2 islarge compared to the capacitance of either or both capacitor C3 orcapacitor C1, or because of the short pulse widths of the pulses, thecapacitor C2 may take a number of pulses from the high voltage pulser tofully charge. Once the capacitor C2 is fully charged the circuit reachesa steady state, as shown by the waveforms in FIG. 2.

In steady state and when the switch S1 is open, the capacitor C2 ischarged and slowly dissipates through the resistive output stage 102, asshown by the slightly rising slope of waveform 210. Once the capacitorC2 is charged and while the switch S1 is open, the voltage at thesurface of the waver (the point between capacitor C2 and capacitor C3)is negative. This negative voltage may be the negative value of thevoltage of the pulses provided by the pulser stage 101. For the examplewaveform shown in FIG. 2, the voltage of each pulse is about 4 kV; andthe steady state voltage at the wafer is about −4 kV. This results in anegative potential across the plasma (e.g., across capacitor C3) thataccelerates positive ions from the plasma to the surface of the wafer.While the switch S1 is open, the charge on capacitor C2 slowlydissipates through the resistive output stage.

When the switch S1 is changed from opened to closed, the voltage acrossthe capacitor C2 may flip (the pulse from the pulser is high as shown inwaveform 205) as the capacitor C2 is charged. In addition, the voltageat the circuit point 123 (e.g., at the surface of the wafer) changes toabout zero as the capacitor C2 charges, as shown in waveform 210. Thus,the pulses from the high voltage pulser can produce a plasma potential(e.g., a potential in the plasma) that rise from a negative high voltageto zero and returns to the negative high voltage at high frequencies,with any or all of fast rise times, fast fall times, or short pulsewidths.

In some embodiments, the action of the resistive output stage 102,elements represented by the resistive output stage 102, that may rapidlydischarge the stray capacitance C1, and may allow the voltage at thepoint between capacitor C2 and capacitor C3 to rapidly return to itssteady negative value of about −4 kV as shown by waveform 210. Theresistive output stage may allow the voltage at the point betweencapacitor C2 and capacitor C3 to exists for about % of the time, andthus maximizes the time which ions are accelerated into the wafer. Insome embodiments, the components contained within the resistive outputstage may be specifically selected to optimize the time during which theions are accelerated into the wafer, and to hold the voltage during thistime approximately constant. Thus, for example, a short pulse with fastrise time and a fast fall time may be useful, so there can be a longperiod of fairly uniform negative potential.

In some embodiments, a bias compensation subsystem can be used to adjustthe chucking voltage in a semiconductor fabrication wafer chamber. Forinstance, a chucking voltage can be applied to the chuck to track thattracks the on/off pattern of the bursts to ensure a constant voltage onthe chuck.

In some embodiments, any of the various high voltage power systems mayinclude a resistive output stage disclosed in this document may includeany or all components, arrangements, functionality, etc. shown ordescribed in U.S. patent application Ser. No. 15/941,731, titled “HighVoltage Resistive Output Stage Circuit” filed on Mar. 30, 2018, which isincorporated in its entirety herein for all purposes.

FIG. 3 is a circuit diagram of a high voltage power system with a plasmaload 300 according to some embodiments. The high voltage power systemwith a plasma load 300 is similar to high voltage power system with aplasma load 100. The pulser stage 110 in this example includes a highvoltage switch S1. In some embodiments, the high voltage switch S1 mayinclude a plurality of switches arranged in series to collectively openand close high voltages. For example, the high voltage switch S1 mayinclude the high voltage switch 1500 described in FIG. 15. As anotherexample, the high voltage switch S1 may, for example, include any switchdescribed in U.S. patent application Ser. No. 16/178,565, filed Nov. 1,2018, titled “High Voltage Switch with Isolated Power,” which isincorporated into this disclosure in its entirety for all purposes.

In any embodiment, a pulser stage 101 or pulser stage 110 may be used toproduce high voltage pulses. In addition, the pulser stage 101 and thepulser stage 110 may be interchangeable.

In this example, the DC bias circuit 104 does not include any biascompensation.

In some embodiments, the pulser stage 110 may produce pulses with avoltage greater than 1 kV, 10 kV, 20 kV, 50 kV, 100 kV, 1,000 kV, etc.,with rise times less than about 1 ns, 10 ns, 50 ns, 100 ns, 250 ns, 500ns, 1,000 ns, etc. with fall times less than about 1 ns, 10 ns, 50 ns,100 ns, 250 ns, 500 ns, 1,000 ns, etc. and frequencies greater thanabout 1 kHz, 10 kHz, 100 kHz, 200 kHz, 500 kHz, 1 MHz, etc.

In some embodiments, the pulser stage 101 may include a radio-frequencypower supply such as, for example, an RF generator.

FIG. 4 shows example waveforms produced by a high voltage power system(e.g., high voltage power system with a plasma load 100 or high voltagepower system with a plasma load 300). The wafer waveform 405 representsthe voltage on the wafer and chuck waveform 410 is the voltage on thechuck. The wafer waveform 405 is measured at the position labeled 122 onthe circuit diagram in FIG. 3. The chuck waveform 410 is measured at theposition labeled 121 on the circuit diagram in FIG. 3. As shown, duringpulsing, the difference between the chuck waveform 410 and the waferwaveform 405 is about 4 kV. With peak voltages above 2 kV, this maycause damage to the wafer on the chuck within a chamber.

The waveforms in FIG. 4 show six burst of about 10 seconds with aplurality of pulse within each burst.

FIG. 5 is a circuit diagram of a high voltage power system with a plasmaload 500 according to some embodiments. The high voltage power systemwith the plasma load 500 is similar to the high voltage power systemwith a plasma load 300.

In this example, the bias compensation circuit 114 is a passive biascompensation circuit and can include a bias compensation diode 505 and abias compensation capacitor 510. The bias compensation diode 505 can bearranged in series with offset supply voltage V1. The bias compensationcapacitor 510 can be arranged across either or both the offset supplyvoltage V1 and the resistor R2. The bias compensation capacitor 510 canhave a capacitance less than 100 nF to 100 μF such as, for example,about 100 μF, 50 μF, 25 μF, 10 μF, 2 μF, 500 nF, 200 nF, etc.

In some embodiments, the bias compensation diode 505 can conductcurrents of between 10 A and 1 kA at a frequency of between 10 Hz and 10kHz.

In some embodiments, the bias capacitor C12 may allow for a voltageoffset between the output of the pulser stage 101 (e.g., at the positionlabeled 125) and the voltage on the electrode (e.g., at the positionlabeled 124). In operation, the electrode may, for example, be at a DCvoltage of −2 kV during a burst, while the output of the nanosecondpulser alternates between +6 kV during pulses and 0 kV between pulses.

In some embodiments, the bias compensation capacitor 510 and the biascompensation diode 505 may allow for the voltage offset between theoutput of the pulser stage 101 (e.g., at the position labeled 125) andthe voltage on the electrode (e.g., at the position labeled 124) to beestablished at the beginning of each burst, reaching the neededequilibrium state. For example, charge is transferred from capacitor C12into capacitor 510 at the beginning of each burst, over the course of aplurality of pulses (e.g., maybe about 5-100), establishing the correctvoltages in the circuit.

FIG. 6 shows example waveforms produced by the high voltage power systemwith the plasma load 500. As shown in the figure, the voltage biasbetween the wafer waveform 605 and the chuck waveform 610 stays fixedduring pulse burst but stays charged after the burst. In this example,the difference between the wafer waveform 605 and the chuck waveform 610during pulsing is less than about 2 kV, which may be within acceptabletolerances. In this example, however, the difference between the waferwaveform 605 and the chuck waveform 610 between pulses is greater thanabout 7 kV, which may not be within acceptable tolerances.

The waveforms in FIG. 6 show six burst of about 10 seconds with aplurality of pulse within each burst.

FIG. 7 is a circuit diagram of a high voltage power system with a plasmaload 700 according to some embodiments. The high voltage power systemwith a plasma load 700 is similar to high voltage power system with theplasma load 500, and includes a second pulser circuit 705.

The second pulser circuit 705 may include the bias compensation circuit114 or components similar to the bias compensation circuit 114.

The second pulser circuit 705, can include a second pulser 701. Thesecond pulser 701, for example, may include one or more or all thecomponents of the pulser stage 110 shown in either FIG. 1 or FIG. 3. Forexample, the pulser stage 110 may include a nanosecond pulser or a highvoltage switch as disclosed in this document (e.g., FIG. 15 and relatedparagraphs). In some embodiments, the second pulser 701 may beconfigured to turn off when the pulser stage 101 is pulsing (e.g.,during bursts), and the second pulser 701 may be configured to turned onwhen the pulser stage 101 is not pulsing (e.g., in between bursts)

The second pulser circuit 705 may also include inductor L9 on thesecondary side of the transformer T2 and switch 710 may be coupled withvoltage source V6. The inductor L9 may represent the stray inductance ofthe second pulser circuit 705 and may have a low inductance such as, forexample, an inductance less than about 500 nH, 250 nH, 100 nH, 50 nH, 25nH, etc. In some embodiments, the voltage source V6 may represent atrigger for the switch 710.

In some embodiments, the second pulser circuit 705 may include theblocking diode D7. The blocking diode D7, for example, may ensurecurrent flows from the switch 710 to the load stage 106. The capacitorC14, for example, may represent the stray capacitance of the blockingdiode D7. The capacitance of capacitor C14, for example, may have a lowcapacitance such as, for example, less than about 1 nF, 500 pF, 200 pF,100 pF, 50 pF, 25 pF, etc.

In some embodiments, the switch 710 may be open while the pulser stage110 is pulsing and closed when the pulser stage 110 is not pulsing tooffset (or bias) the voltage provided by the pulser stage.

In some embodiments, the switch 710 may include a plurality of switchesarranged in series to collectively open and close high voltages. In someembodiments, the switch 710 may include the high voltage switch 1500described in FIG. 15. As another example, the high voltage switch 905may, for example, include any switch described in U.S. patentapplication Ser. No. 16/178,565, filed Nov. 1, 2018, titled “HighVoltage Switch with Isolated Power,” which is incorporated into thisdisclosure in its entirety for all purposes.

FIG. 8 shows example waveforms produced by the high voltage power systemwith a plasma load 700. The wafer waveform 805 represents the voltage onthe wafer and chuck waveform 810 is the voltage on the chuck. The waferwaveform 805 is measured at wafer which is indicated by the positionlabeled 122 on the circuit diagram in FIG. 7. The chuck waveform 810 ismeasured at the chuck which is indicated by the position 121 on thecircuit diagram in FIG. 7. The bias waveform 815 is measured at theposition labeled 124 on the circuit diagram in FIG. 7. In this example,the bias capacitor 510 is discharging and may require the second pulsercircuit 705 to include a higher power supply than V2, for example, inorder to recharge the bias capacitor, which may require severalkilowatts of power.

The waveforms in FIG. 8 show six burst of about 10 seconds with aplurality of pulse within each burst.

FIG. 9 is a circuit diagram of a high voltage power system with a plasmaload 900 according to some embodiments. The high voltage power systemwith a plasma load 500 is similar to high voltage power system with aplasma load 900.

In this embodiment, the bias compensation circuit 914, can include ahigh voltage switch 905 coupled across the bias compensation diode 505and coupled with power supply V1. In some embodiments, the high voltageswitch 905 may include a plurality of switches 905 arranged in series tocollectively open and close high voltages. For example, the high voltageswitch 905 may include the high voltage switch 1500 described in FIG.15. In some embodiments, the high voltage switch 905 may be coupled witha switch trigger V4.

The high voltage switch 905 may be coupled in series with either or bothan inductor L9 and a resistor R11. The inductor L9 may limit peakcurrent through high voltage switch 905. The inductor L9, for example,may have an inductance less than about 100 pH such as, for example,about 250 pH, 100 pH, 50 pH, 25 pH, 10 pH, 5 pH, 1 μH, etc. The resistorR11, for example, may shift power dissipation to the resistive outputstage 102. The resistance of resistor R11, for example, may have aresistance of less than about 1,000 ohms, 500 ohms, 250 ohms, 100 ohms,50 ohms, 10 ohms, etc.

In some embodiments, the high voltage switch 905 may include a snubbercircuit. The snubber circuit may include resistor R9, snubber diode D8,snubber capacitor C15, and snubber resistor R10.

In some embodiments, the resistor R8 can represent the stray resistanceof the offset supply voltage V1. The resistor R8, for example, may havea high resistance such as, for example, a resistance of about 10 kOhm,100 kOhm, 1 MOhm, 10 MOhm, 100 MOhm, 1 GOhm, etc.

In some embodiments, the high voltage switch 905 may include a pluralityof switches arranged in series to collectively open and close highvoltages. For example, the high voltage switch 905 may include the highvoltage switch 1500 described in FIG. 15. As another example, the highvoltage switch 905 may, for example, include any switch described inU.S. patent application Ser. No. 16/178,565, filed Nov. 1, 2018, titled“High Voltage Switch with Isolated Power,” which is incorporated intothis disclosure in its entirety for all purposes.

In some embodiments, the high voltage switch 905 may be open while thepulser stage 110 is pulsing and closed when the pulser stage 110 is notpulsing. When the high voltage switch 905 is closed, for example,current can short across the bias compensation diode 505. Shorting thiscurrent may allow the bias between the wafer and the chuck to be lessthan 2 kV, which may be within acceptable tolerances.

In some embodiments, the high voltage switch 905 can allow the electrodevoltage (the position labeled 124) and the wafer voltage (the positionlabeled 122) to be quickly restored (e.g., less than about 100 ns, 200ns, 500 ns, 1 μs) to the chucking potential (the position labeled 121).This is shown, for example, in FIGS. 10, 11A, and 11B.

FIG. 10 shows example waveforms produced by the high voltage powersystem with a plasma load 900 according to some embodiments. The waferwaveform 1005 represents the voltage on the wafer, the chuck waveform1010 represents the voltage on the chuck, and the bias waveform 1015represents the voltage from the bias compensation circuit 114. The waferwaveform 1005 is measured at the position labeled 122 on the circuitdiagram in FIG. 9. The chuck waveform 1010 is measured at the positionlabeled 121 on the circuit diagram in FIG. 9. The bias waveform 1015 ismeasured at the position labeled 124 on the circuit diagram in FIG. 9.

The waveforms in FIG. 10 show six burst of about 10 seconds with aplurality of pulse within each burst.

FIG. 11A and FIG. 11B show example waveforms from a high voltage powersystem with a plasma load 900 according to some embodiments. FIG. 11Ashows a single burst having 340 pulses and FIG. 11B shows a few pulseswithin a burst. The waveform 1105 shows the voltage at the electrode(the position labeled 124 in FIG. 9) and the waveform 1110 shows thevoltage at the wafer (the position labeled 122 in FIG. 9). Note that thevoltages on the electrode and wafer tend to track with a constant offsetof about 2 kV. The waveforms also show how the voltages return to DCvalue while the pulser is off until the next burst begins some timelater.

FIG. 12 is a circuit diagram of a high voltage power system with aplasma load 1200 according to some embodiments. The high voltage powersystem with a plasma load 1200 is similar to high voltage power systemwith a plasma load 900.

In some embodiments, the bias compensation circuit 1214, can include afour high voltage switch stages (including switches 1220, 1225, 1230,and 1235) arranged across or in parallel with the bias compensationdiode 505. Each switch stage includes a switch (e.g., switches 1220,1225, 1230, and 1235) and a voltage sharing resistor (e.g., resistorR15, R16, R17, and R18). Either or both the resistor R11 and theinductor L7 are arranged in series with the switch stages. The inductorL9, for example, may have an inductance less than about 100 pH such as,for example, about 1 mH, 500 pH, 250 pH, 100 pH, 50 pH, 25 pH, 10 pH, 5μH, 1 pH, etc. In some embodiments, the switches 1220, 1225, 1230, and1235 may be open while the pulser stage 110 is pulsing and closed whenthe pulser stage 110 is not pulsing. When the switches 1220, 1225, 1230,and 1235 are closed, for example, current can short across the biascompensation diode 505. Shorting this current may allow the bias betweenthe wafer and the chuck to be less than 2 kV, which may be withinacceptable tolerances.

Each switch 1220, 1225, 1230, and 1235 may include a plurality ofswitches arranged in series to collectively open and close highvoltages. For example, each switch 1220, 1225, 1230, and 1235 maycollectively or individually, for example, include the high voltageswitch 1500 described in FIG. 15. As another example, each switch 1220,1225, 1230, and 1235 may collectively or individually, for example,include any switch described in U.S. patent application Ser. No.16/178,565, filed Nov. 1, 2018, titled “High Voltage Switch withIsolated Power,” which is incorporated into this disclosure in itsentirety for all purposes.

In some embodiments, the voltage sharing resistors (e.g., resistor R15,R16, R17, and R18) may have a high resistance such as, for example, aresistance of about 1 kOhm, 10 kOhm, 100 kOhm, 1 MOhm, 10 MOhm, 100MOhm, etc

In this example, four high voltage switch stages are shown, any numberof high voltage switch stages may be used.

FIG. 13 is a circuit diagram of a high voltage power system with aplasma load 1300 according to some embodiments. The high voltage powersystem with a plasma load 1300 is similar to high voltage power systemwith a plasma load 1200.

In this example, the bias compensation circuit 1314 is similar to thebias compensation circuit 1214. In this example, each switch module(1220, 1225, 1230, and 1235) with the bias compensation circuit 1314 mayinclude a corresponding snubber circuit. Each snubber circuit caninclude a snubber diode and a snubber capacitor. In some embodiments,the snubber diode may include a snubber resistor arranged across thesnubber diode. Each switch module may include a resistor which mayensure that the voltage is shared evenly between each of the switchesarranged in series.

FIG. 14 is a circuit diagram of a high voltage power system with aplasma load 1400 according to some embodiments. The high voltage powersystem with a plasma load 1400 is similar to high voltage power systemwith a plasma load 900. In this example, the bias compensation circuit1414 does not include a snubber circuit. In this example, the biascompensation circuit 1414 includes a bias compensation inductor 1420that is arranged in series with the switch S4. The inductor 1420 mayhave an inductance less than about 300 nH, 100 nH, 10 nH, 1 nH, etc.

In some embodiments, the switch S4 may include the high voltage switch1500 described in FIG. 15. As another example, the switch S4 may, forexample, include any switch described in U.S. patent application Ser.No. 16/178,565, filed Nov. 1, 2018, titled “High Voltage Switch withIsolated Power,” which is incorporated into this disclosure in itsentirety for all purposes.

FIG. 15 is a block diagram of a high voltage switch 1500 with isolatedpower according to some embodiments. The high voltage switch 1500 mayinclude a plurality of switch modules 1505 (collectively or individually1505, and individually 1505A, 1505B, 1505C, and 1505D) that may switchvoltage from a high voltage source 1560 with fast rise times and/or highfrequencies and/or with variable pulse widths. Each switch module 1505may include a switch 1510 such as, for example, a solid state switch.

In some embodiments, the switch 1510 may be electrically coupled with agate driver circuit 1530 that may include a power supply 1540 and/or anisolated fiber trigger 1545 (also referred to as a gate trigger or aswitch trigger). For example, the switch 1510 may include a collector,an emitter, and a gate (or a drain, a source, and a gate) and the powersupply 1540 may drive the gate of the switch 1510 via the gate drivercircuit 1530. The gate driver circuit 1530 may, for example, be isolatedfrom the other components of the high voltage switch 1500.

In some embodiments, the power supply 1540 may be isolated, for example,using an isolation transformer. The isolation transformer may include alow capacitance transformer. The low capacitance of the isolationtransformer may, for example, allow the power supply 1540 to charge onfast time scales without requiring significant current. The isolationtransformer may have a capacitance less than, for example, about 100 pF.As another example, the isolation transformer may have a capacitanceless than about 30-100 pF. In some embodiments, the isolationtransformer may provide voltage isolation up to 1 kV, 5 kV, 10 kV, 25kV, 50 kV, etc.

In some embodiments, the isolation transformer may have a low straycapacitance. For example, the isolation transformer may have a straycapacitance less than about 1,000 pF, 100 pF, 10 pF, etc. In someembodiments, low capacitance may minimize electrical coupling to lowvoltage components (e.g., the source of the input control power) and/ormay reduce EMI generation (e.g., electrical noise generation). In someembodiments, the transformer stray capacitance of the isolationtransformer may include the capacitance measured between the primarywinding and secondary winding.

In some embodiments, the isolation transformer may be a DC to DCconverter or an AC to DC transformer. In some embodiments, thetransformer, for example, may include a 110 V AC transformer.Regardless, the isolation transformer can provide isolated power fromother components in the high voltage switch 1500. In some embodiments,the isolation may be galvanic, such that no conductor on the primaryside of the isolation transformer passes through or makes contact withany conductor on the secondary side of the isolation transformer.

In some embodiments, the transformer may include a primary winding thatmay be wound or wrapped tightly around the transformer core. In someembodiments, the primary winding may include a conductive sheet that iswrapped around the transformer core. In some embodiments, the primarywinding may include one or more windings.

In some embodiments, a secondary winding may be wound around the core asfar from the core as possible. For example, the bundle of windingscomprising the secondary winding may be wound through the center of theaperture in the transformer core. In some embodiments, the secondarywinding may include one or more windings. In some embodiments, thebundle of wires comprising the secondary winding may include a crosssection that is circular or square, for example, to minimize straycapacitance. In some embodiments, an insulator (e.g., oil or air) may bedisposed between the primary winding, the secondary winding, or thetransformer core.

In some embodiments, keeping the secondary winding far from thetransformer core may have some benefits. For example, it may reduce thestray capacitance between the primary side of the isolation transformerand secondary side of the isolation transformer. As another example, itmay allow for high voltage standoff between the primary side of theisolation transformer and the secondary side of the isolationtransformer, such that corona and/or breakdown is not formed duringoperation.

In some embodiments, spacings between the primary side (e.g., theprimary windings) of the isolation transformer and the secondary side ofthe isolation transformer (e.g., the secondary windings) can be about0.1″, 0.5″, 1″, 5″, or 10″. In some embodiments, typical spacingsbetween the core of the isolation transformer and the secondary side ofthe isolation transformer (e.g., the secondary windings) can be about0.1″, 0.5″, 1″, 5″, or 10″. In some embodiments, the gap between thewindings may be filled with the lowest dielectric material possible suchas, for example, vacuum, air, any insulating gas or liquid, or solidmaterials with a relative dielectric constant less than 3.

In some embodiments, the power supply 1540 may include any type of powersupply that can provide high voltage standoff (isolation) or have lowcapacitance (e.g., less than about 1,000 pF, 100 pF, 10 pF, etc.). Insome embodiments, the control voltage power source may supply 1520 VACor 240 VAC at 60 Hz.

In some embodiments, each power supply 1540 may be inductivelyelectrically coupled with a single control voltage power source. Forexample, the power supply 1540A may be electrically coupled with thepower source via a first transformer; the power supply 1540B may beelectrically coupled with the power source via a second transformer; thepower supply 1540C may be electrically coupled with the power source viaa third transformer; and the power supply 1540D may be electricallycoupled with the power source via a fourth transformer. Any type oftransformer, for example, may be used that can provide voltage isolationbetween the various power supplies.

In some embodiments, the first transformer, the second transformer, thethird transformer, and the fourth transformer may comprise differentsecondary winding around a core of a single transformer. For example,the first transformer may comprise a first secondary winding, the secondtransformer may comprise a second secondary winding, the thirdtransformer may comprise a third secondary winding, and the fourthtransformer may comprise a fourth secondary winding. Each of thesesecondary winding may be wound around the core of a single transformer.In some embodiments, the first secondary winding, the second secondarywinding, the third secondary winding, the fourth secondary winding, orthe primary winding may comprise a single winding or a plurality ofwindings wound around the transformer core.

In some embodiments, the power supply 1540A, the power supply 1540B, thepower supply 1540C, and/or the power supply 1540D may not share a returnreference ground or a local ground.

The isolated fiber trigger 1545, for example, may also be isolated fromother components of the high voltage switch 1500. The isolated fibertrigger 1545 may include a fiber optic receiver that allows each switchmodule 1505 to float relative to other switch modules 1505 and/or theother components of the high voltage switch 1500, and/or, for example,while allowing for active control of the gates of each switch module1505.

In some embodiments, return reference grounds or local grounds or commongrounds for each switch module 1505, for example, may be isolated fromone another, for example, using an isolation transformer.

Electrical isolation of each switch module 1505 from common ground, forexample, can allow multiple switches to be arranged in a seriesconfiguration for cumulative high voltage switching. In someembodiments, some lag in switch module timing may be allowed ordesigned. For example, each switch module 1505 may be configured orrated to switch 1 kV, each switch module may be electrically isolatedfrom each other, and/or the timing of closing each switch module 1505may not need to be perfectly aligned for a period of time defined by thecapacitance of the snubber capacitor and/or the voltage rating of theswitch.

In some embodiments, electrical isolation may provide many advantages.One possible advantage, for example, may include minimizing switch toswitch jitter and/or allowing for arbitrary switch timing. For example,each switch 1510 may have switch transition jitters less than about 500ns, 50 ns, 20 ns, 5 ns, etc.

In some embodiments, electrical isolation between two components (orcircuits) may imply extremely high resistance between two componentsand/or may imply a small capacitance between the two components.

Each switch 1510 may include any type of solid state switching devicesuch as, for example, an IGBT, a MOSFET, a SiC MOSFET, SiC junctiontransistor, FETs, SiC switches, GaN switches, photoconductive switch,etc. The switch 1510, for example, may be able to switch high voltages(e.g., voltages greater than about 1 kV), with high frequency (e.g.,greater than 1 kHz), at high speeds (e.g., a repetition rate greaterthan about 500 kHz) and/or with fast rise times (e.g., a rise time lessthan about 25 ns) and/or with long pulse lengths (e.g., greater thanabout 10 ms). In some embodiments, each switch may be individually ratedfor switching 1,200 V-1,700 V, yet in combination can switch greaterthan 4,800 V-6,800 V (for four switches). Switches with various othervoltage ratings may be used.

There may be some advantages to using a large number of lower voltageswitches rather than a few higher voltage switches. For example, lowervoltage switches typically have better performance: lower voltageswitches may switch faster, may have faster transition times, and/or mayswitch more efficiently than high voltage switches. However, the greaterthe number of switches the greater the timing issues that may berequired.

The high voltage switch 1500 shown in FIG. 15 includes four switchmodules 1505. While four are shown in this figure, any number of switchmodules 1505 may be used such as, for example, two, eight, twelve,sixteen, twenty, twenty-four, etc. For example, if each switch in eachswitch module 1505 is rated at 1200 V, and sixteen switches are used,then the high voltage switch can switch up to 19.2 kV. As anotherexample, if each switch in each switch module 1505 is rated at 1700 V,and sixteen switches are used, then the high voltage switch can switchup to 27.2 kV.

In some embodiments, the high voltage switch 1500 may include a fastcapacitor 1555. The fast capacitor 1555, for example, may include one ormore capacitors arranged in series and/or in parallel. These capacitorsmay, for example, include one or more polypropylene capacitors. The fastcapacitor 1555 may store energy from the high voltage source 1560.

In some embodiments, the fast capacitor 1555 may have low capacitance.In some embodiments, the fast capacitor 1555 may have a capacitancevalue of about 1 μF, about 5 μF, between about 1 μF and about 5 μF,between about 100 nF and about 1,000 nF etc.

In some embodiments, the high voltage switch 1500 may or may not includea crowbar diode 1550. The crowbar diode 1550 may include a plurality ofdiodes arranged in series or in parallel that may, for example, bebeneficial for driving inductive loads. In some embodiments, the crowbardiode 1550 may include one or more Schottky diodes such as, for example,a silicon carbide Schottky diode. The crowbar diode 1550 may, forexample, sense whether the voltage from the switches of the high voltageswitch is above a certain threshold. If it is, then the crowbar diode1550 may short the power from switch modules to ground. The crowbardiode, for example, may allow an alternating current path to dissipateenergy stored in the inductive load after switching. This may, forexample, prevent large inductive voltage spikes. In some embodiments,the crowbar diode 1550 may have low inductance such as, for example, 1nH, 10 nH, 100 nH, etc. In some embodiments, the crowbar diode 1550 mayhave low capacitance such as, for example, 100 pF, 1 nF, 10 nF, 100 nF,etc.

In some embodiments, the crowbar diode 1550 may not be used such as, forexample, when the load 1565 is primarily resistive.

In some embodiments, each gate driver circuit 1530 may produce less thanabout 1000 ns, 100 ns, 10.0 ns, 5.0 ns, 3.0 ns, 1.0 ns, etc. of jitter.In some embodiments, each switch 1510 may have a minimum switch on time(e.g., less than about 10 μs, 1 μs, 500 ns, 100 ns, 50 ns, 10, 5 ns,etc.) and a maximum switch on time (e.g., greater than 25 s, 10 s, 5 s,1 s, 500 ms, etc.).

In some embodiments, during operation each of the high voltage switchesmay be switched on and/or off within 1 ns of each other.

In some embodiments, each switch module 1505 may have the same orsubstantially the same (±5%) stray inductance. Stray inductance mayinclude any inductance within the switch module 1505 that is notassociated with an inductor such as, for example, inductance in leads,diodes, resistors, switch 1510, and/or circuit board traces, etc. Thestray inductance within each switch module 1505 may include lowinductance such as, for example, an inductance less than about 300 nH,100 nH, 10 nH, 1 nH, etc. The stray inductance between each switchmodule 1505 may include low inductance such as, for example, aninductance less than about 300 nH, 100 nH, 10 nH, 1 nH, etc.

In some embodiments, each switch module 1505 may have the same orsubstantially the same (±5%) stray capacitance. Stray capacitance mayinclude any capacitance within the switch module 1505 that is notassociated with a capacitor such as, for example, capacitance in leads,diodes, resistors, switch 1510 and/or circuit board traces, etc. Thestray capacitance within each switch module 1505 may include lowcapacitance such as, for example, less than about 1,000 pF, 100 pF, 10pF, etc. The stray capacitance between each switch module 1505 mayinclude low capacitance such as, for example, less than about 1,000 pF,100 pF, 10 pF, etc.

Imperfections in voltage sharing can be addressed, for example, with apassive snubber circuit (e.g., the snubber diode 1515, the snubbercapacitor 1520, and/or the freewheeling diode 1525). For example, smalldifferences in the timing between when each of the switches 1510 turn onor turn off or differences in the inductance or capacitances may lead tovoltage spikes. These spikes can be mitigated by the various snubbercircuits (e.g., the snubber diode 1515, the snubber capacitor 1520,and/or the freewheeling diode 1525).

A snubber circuit, for example, may include a snubber diode 1515, asnubber capacitor 1520, a snubber resistor 116, and/or a freewheelingdiode 1525. In some embodiments, the snubber circuit may be arrangedtogether in parallel with the switch 1510. In some embodiments, thesnubber capacitor 1520 may have low capacitance such as, for example, acapacitance less than about 100 pF.

In some embodiments, the high voltage switch 1500 may be electricallycoupled with or include a load 1565 (e.g., a resistive or capcitive orinductive load). The load 1565, for example, may have a resistance from50 ohms to 500 ohms. Alternatively or additionally, the load 1565 may bean inductive load or a capacitive load.

FIG. 16 shows example waveforms 1600 from a high voltage power systemaccording to some embodiments. The waveforms 1600 were produced from ahigh voltage power system producing a positive 2 kV bias (e.g., offsetsupply voltage V1 produces 2 kV) and outputs a signal with a peakvoltage of 7 kV. In this example, a high voltage switch (e.g., highvoltage switch 905) is included with the high voltage power system andis closed while the pulser stage is pulsing and open while the pulserstage is not pulsing.

The waveform 1605 represents the voltage from the pulser stage 101. Thewaveform 1610 represents the electrode voltage measured from ground tocircuit point 124. The waveform 1615 represents the wafer voltagemeasured from ground to circuit point 122. The waveform 1620 representsthe current through the bias compensation circuit 114.

The waveforms 1600 show the last pulse of a burst and the circuitreturning to steady state after the burst. The waveform 1600 shows acontinuous 2 kV offset between the electrode voltage and the wafervoltage. This offset voltage is the chucking voltage, and maintaining acontinuous 2 kV chucking voltage as shown may be within the thresholdrequired to avoid damage to the wafer.

FIG. 17 shows example waveforms 1700 from a high voltage power systemaccording to some embodiments. The waveforms 1700 were produced from ahigh voltage power system producing a positive 2 kV bias (e.g., offsetsupply voltage V1 produces 2 kV) and outputs a signal with a peakvoltage of 6 kV. In this example, a high voltage switch (e.g., highvoltage switch 905) is included with the high voltage power system andis closed while the pulser stage is pulsing and open while the pulserstage is not pulsing.

The waveform 1705 represents the voltage from the pulser stage 101. Thewaveform 1710 represents the electrode voltage measured from ground tocircuit point 124. The waveform 1715 represents the wafer voltagemeasured from ground to circuit point 122. The waveform 1720 representsthe current through the bias compensation circuit 114.

The waveforms 1700 show all the pulses within a burst.

FIG. 18 shows example waveforms 1800 from a high voltage power systemaccording to some embodiments. The waveforms 1700 were produced from ahigh voltage power system producing a positive 2 kV bias (e.g., offsetsupply voltage V1 produces 2 kV) and outputs a signal with a peakvoltage of 6 kV. In this example, a high voltage switch (e.g., highvoltage switch 905) is not used. Without the high voltage switchenabling bias compensation, the waveforms 1800 shows that a constant 2kV chucking voltage is not maintained at the end of the burst.

The waveform 1805 represents the voltage from the pulser stage 101. Thewaveform 1810 represents the electrode voltage measured from ground tocircuit point 124. The waveform 1815 represents the wafer voltagemeasured from ground to circuit point 122. The waveform 1820 representsthe current through the bias compensation circuit 114.

The waveforms 1800 show all the pulses within a burst.

FIG. 19 is a circuit diagram of a high voltage power system with aplasma load 1900 according to some embodiments. The high voltage powersystem with the plasma load 1900 is similar to the high voltage powersystem with a plasma load 500 shown in FIG. 5. In this example, theresistive output stage 102 is removed and an energy recovery circuit1905 has been added.

In this example, the energy recovery circuit 1905 may be positioned onor electrically coupled with the secondary side of the transformer T1.The energy recovery circuit 1905, for example, may include a diode 1930(e.g., a crowbar diode) across the secondary side of the transformer T1.The energy recovery circuit 1905, for example, may include diode 1910and inductor 1915 (arranged in series), which can allow current to flowfrom the secondary side of the transformer T1 to charge the power supplyC7. The diode 1910 and the inductor 1915 may be electrically connectedwith the secondary side of the transformer T1 and the power supply C7.In some embodiments, the energy recovery circuit 1905 may include diode1935 and/or inductor 1940 electrically coupled with the secondary of thetransformer T1. The inductor 1940 may represent the stray inductanceand/or may include the stray inductance of the transformer T1.

When the nanosecond pulser is turned on, current may charge the loadstage 106 (e.g., charge the capacitor C3, capacitor C2, or capacitorC9). Some current, for example, may flow through inductor 1915 when thevoltage on the secondary side of the transformer T1 rises above thecharge voltage on the power supply C7. When the nanosecond pulser isturned off, current may flow from the capacitors within the load stage106 through the inductor 1915 to charge the power supply C7 until thevoltage across the inductor 1915 is zero. The diode 1930 may prevent thecapacitors within the load stage 106 from ringing with the inductance inthe load stage 106 or the bias compensation circuit 104.

The diode 1910 may, for example, prevent charge from flowing from thepower supply C7 to the capacitors within the load stage 106.

The value of inductor 1915 can be selected to control the current falltime. In some embodiments, the inductor 1915 can have an inductancevalue between 1 μH-500 μH.

In some embodiments, the energy recovery circuit 1905 may include aswitch that can be used to control the flow of current through theinductor 1915. The switch, for example, may be placed in series with theinductor 1915. In some embodiments, the switch may be closed when theswitch S1 is open and/or no longer pulsing to allow current to flow fromthe load stage 106 back to the high voltage load C7. The switch, forexample, may include a high voltage switch such as, for example, thehigh voltage switch 1500.

The energy recovery circuit 1905 may be added to the high voltage powersystem with a plasma load 700, the high voltage power system with aplasma load 900, the high voltage power system with a plasma load 1200,the high voltage power system with a plasma load 1300, or the highvoltage power system with a plasma load 1400; and/or the resistiveoutput stage 102 may be removed from any of these circuits.

In some embodiments, the pulser stage 101 may include the high voltageswitch 1500 in place of or in addition to the various components shownin pulser stage 101. In some embodiments, using a high voltage switch1500 may allow for removal of at least the transformer T1 and the switchS1.

Unless otherwise specified, the term “substantially” means within 5% or10% of the value referred to or within manufacturing tolerances. Unlessotherwise specified, the term “about” means within 5% or 10% of thevalue referred to or within manufacturing tolerances.

Numerous specific details are set forth herein to provide a thoroughunderstanding of the claimed subject matter. However, those skilled inthe art will understand that the claimed subject matter may be practicedwithout these specific details. In other instances, methods, apparatusesor systems that would be known by one of ordinary skill have not beendescribed in detail so as not to obscure claimed subject matter.

The use of “adapted to” or “configured to” herein is meant as open andinclusive language that does not foreclose devices adapted to orconfigured to perform additional tasks or steps. Additionally, the useof “based on” is meant to be open and inclusive, in that a process,step, calculation, or other action “based on” one or more recitedconditions or values may, in practice, be based on additional conditionsor values beyond those recited. Headings, lists, and numbering includedherein are for ease of explanation only and are not meant to belimiting.

While the present subject matter has been described in detail withrespect to specific embodiments thereof, it will be appreciated thatthose skilled in the art, upon attaining an understanding of theforegoing, may readily produce alterations to, variations of, andequivalents to such embodiments. Accordingly, it should be understoodthat the present disclosure has been presented for purposes of examplerather than limitation, and does not preclude inclusion of suchmodifications, variations, or additions to the present subject matter aswould be readily apparent to one of ordinary skill in the art.

That which is claimed:
 1. A high voltage power system comprising: a highvoltage pulsing power supply; a transformer electrically coupled withthe high voltage pulsing power supply; an output electrically coupledwith the transformer and configured to output high voltage pulses withan amplitude greater than 1 kV and a pulse repetition frequency greaterthan 1 kHz; and a bias compensation circuit arranged in parallel withthe output the bias compensation circuit comprising: a bias compensationdiode; and a DC power supply arranged in series with the biascompensation diode.
 2. The high voltage power system according to claim1, further comprising a bias compensation capacitor arranged across atleast the DC power supply having a capacitance less than about 10 μF. 3.The high voltage power system according to claim 1, wherein the highvoltage pulsing power supply comprises a nanosecond pulser and atransformer.
 4. The high voltage power system according to claim 1,wherein the high voltage power supply comprises a plurality of switchesarranged in series and a transformer.
 5. The high voltage power systemaccording to claim 1, wherein the bias compensation circuit comprises ahigh voltage switch disposed across the bias compensation diode, whereinthe high voltage switch is configured to be open when the high voltagepulsing power supply is pulsing, and wherein the high voltage switch isconfigured to be closed when the high voltage pulsing power supply isnot pulsing.
 6. The high voltage power system according to claim 5,wherein the high voltage switch comprises a plurality of switchesarranged in series.
 7. The high voltage power system according to claim5, further comprising an inductor arranged in series with the highvoltage switch having an inductance less than about 1 mH.
 8. The highvoltage power system according to claim 1, wherein the output is coupledwith an electrode that is capacitively coupled with a plasma.
 9. A highvoltage power system comprising: a high voltage pulsing power supply; anoutput electrically coupled with the high voltage pulsing power supplyand configured to output high voltage pulses with an amplitude greaterthan 1 kV and a pulse repetition frequency greater than 2 kHz; a biascompensation diode; a DC power supply arranged in series with the biascompensation diode, the bias compensation diode and the DC power supplyarranged in parallel with the output; and a high voltage switch coupledacross the bias compensation diode, wherein the high voltage switch isconfigured to turn off when the high voltage switching power supply ispulsing, and the high voltage switch is turned on when the high voltageswitching power supply is not pulsing.
 10. The high voltage power systemaccording to claim 9, further comprising a bias compensation capacitorarranged across at least the DC power supply.
 11. The high voltage powersystem according to claim 9, wherein the bias compensation diode, the DCpower supply, and the high voltage switch comprise a bias compensationcircuit that is arranged in the high voltage power system across theoutput.
 12. The high voltage power system according to claim 9, whereinthe output is coupled with an electrode that is capacitively coupledwith a plasma.
 13. The high voltage power system according to claim 9,wherein the high voltage switch is configured to be open when the highvoltage pulsing power supply is pulsing, and wherein the high voltageswitch is configured to be closed when the high voltage pulsing powersupply is not pulsing.
 14. The high voltage power system according toclaim 9, wherein the DC power supply provides −5 kV to +5 kV.
 15. Thehigh voltage power system according to claim 9, wherein the high voltageswitch includes a snubber circuit.
 16. The high voltage power systemaccording to claim 9, wherein the high voltage switch comprises aplurality of switches arranged in series and having a plurality ofvoltage sharing resistors such that each voltage sharing resistor of theplurality of voltage sharing resistors is arranged across acorresponding switch of the plurality of switches.
 17. The high voltagepower system according to claim 9, wherein the bias compensation diodeis configured to conduct between 10 A and 1 kA of current at a frequencyof between 10 Hz and 10 kHz.
 18. The high voltage power system accordingto claim 9, further comprising a bias capacitor electrically coupledwith the high voltage pulsing power supply and the bias compensationdiode, the bias capacitor having a value less than about 10 μF.
 19. Thehigh voltage power system according to claim 9, further comprising aninductor arranged in series with the high voltage switch having aninductance less than about 1 mH.
 20. The high voltage power systemaccording to claim 9, further comprising a resistor arranged in serieswith the high voltage switch having a resistance less than about 1,000mohms.
 21. A method comprising: opening a bias compensation switch thatis arranged in series with a DC power supply, the bias compensationswitch and the DC power supply being arranged across a load; pulsing ahigh voltage power supply with a voltage greater than 1 kV and a pulserepetition frequency greater than 20 kHZ into the load; closing the biascompensation switch; and not pulsing the high voltage power supply. 22.The method according to claim 21, where the load comprises an electrodethat is capacitively coupled with a plasma.